Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$219.42	5.822%	$232.1946	$232.19	$232.20	$232.20
Purchase #2	$92.91	13.404%	$105.3637	$105.36	$105.35	$105.40
Purchase #3	$127.94	13.365%	$145.0392	$145.04	$145.05	$145.00
Purchase #4	$118.30	6.495%	$125.9836	$125.98	$126.00	$126.00
Purchase #5	$174.60	4.712%	$182.8272	$182.83	$182.85	$182.80
Purchase #6	$161.39	6.866%	$172.471	$172.47	$172.45	$172.50
Purchase #7	$203.71	10.234%	$224.5577	$224.56	$224.55	$224.60
7 purchase totals =	$1,098.27		$1,188.4370	$1,188.43	$1,188.45	$1,188.50